High voltage (HV) electrical distribution systems typically use utility poles or towers that support insulators, such as ceramic insulators, and the insulators support conductors that carry the high voltage. The ceramic insulators are affixed to the crossarms by bolts. The HV conductor (typically twisted wire strands) seats in a groove in the insulator and is affixed to the insulator via a metal tie wire. The groove may be on top of the insulator or on the side of the insulator.
Frequently, there are three parallel cables, each carrying a different phase. If there is a short to ground or a short between cables, a fuse or breaker will trip, causing a power outage or a rerouting of the electricity. A lineman must then fix the problem and refuse or reset the fuse/breaker.
FIG. 1 is a perspective view of a conventional ceramic insulator 10 that is mounted on a wooden pole (not shown) using conventional hardware, such as a bracket or a bolt. Round insulators are typically 4-8 inches in diameter. A bare cable 12 (a conductor) is secured to the insulator 10 by a wire (not shown) twisted around the insulator neck 13 and the cable 12. FIG. 2 is a top down view of the insulator 10 and cable 12. For three phase distribution, there are typically two insulators/cables at the ends of a wooden crossarm and one insulator/cable supported in the middle or on the top of the pole.
When there is a straight run of the cable 12, the cable 12 may be supported by the indent 14 at the top of the insulator 10 or may be tied to the side of the neck 13. A twisted wire keeps the cable 12 in place. When the cable path needs to change direction, the cable 12 is bent around the neck 13 of the insulator 10, as shown in FIGS. 1 and 2.
In locations where there are large birds, or other animals, dielectric cable shields (which include an insulator cover) are sometimes used to prevent such birds or animals contacting two or more of the-energized or grounded cables.
Prior art insulator covers for covering the insulator 10 in FIG. 1 are typically designed for the symmetrical insulator/wire configuration, where the cable 12 is supported by the top indent 14 of the insulator 10. If a prior art cover were used with the asymmetrical configuration of FIG. 1, the cover would undesirably seat at an angle over the insulator 10. The cover is somewhat larger than the insulator, so there is some play between the cover and insulator.
Additionally, different conductor diameters may be used with the same type of insulator, where the diameter may be selected based on the required voltage or current transmitted or the distance between poles. This further creates unpredictability in the insulator cover's ability to be properly oriented with respect to the insulator and conductor.
In either the symmetrical or asymmetrical case, the prior art covers are not secured to the insulator 10 and cable 12, and a high wind may catch the open underside of the cover and rotate it with respect to the insulator 10 and cable 12, reducing the effectiveness of the cover in protecting wildlife and preventing shorts. If a cover is rotated, it may jeopardize the leakage distance of the insulator and electrically short the insulator. If a rotated or tilted cover is spotted, a lineman must reorient the cover. The problem with tilted covers is more extreme when the conductor is tied to the side of the insulator, as shown in FIG. 1. In FIG. 1, the rotation point of the cover may be around the off-centered cable 12, so the cover more easily lifts off from the opposite side. This exact problem with prior art insulator covers has been reported to the present inventor by a power company, and the inventor was asked to design an improved insulator/conductor cover that did not rotate about the cable and insulator with high winds.
Therefore, what is needed is a practical cover system for an insulator/cable that can accommodate symmetrical and asymmetrical insulator/cable configurations and which cannot be rotated or even tilted when subjected to high winds.